1. Field of the Invention
The present invention relates to a data integrated circuit (IC) and an apparatus for driving a plasma display panel (PDP) using the same, and more particularly to a data IC capable of improving display quality and an apparatus for driving a PDP using the same.
2. Description of the Background Art
A plasma display panel (PDP) emits light from a fluorescent body by ultraviolet (UV) rays of 147 nm generated when an inactive mixed gas such as He+Xe, Ne+Xe, and He+Xe+Ne is discharged to display images including characters and graphics. Such a PDP is easily made thin and large and provides significantly improved picture quality due to recent development of technology. In particular, wall charges are accumulated on the surface of a three-electrode AC surface discharge type PDP during discharge and electrodes are protected against sputtering generated by discharge such that the three-electrode AC surface discharge type PDP is driven by a low voltage and has a long life.
Referring to FIG. 1, a discharge cell of the three-electrode AC surface discharge type PDP according to a background art includes a scan electrode Y and a sustain electrode Z formed on a top substrate 10 and an address electrode X formed on a bottom substrate 18. The scan electrode Y and the sustain electrode Z include transparent electrodes 12Y and 12Z, and metal bus electrodes 13Y and 13Z having a line width smaller than the line width of the transparent electrodes 12Y and 12Z and formed at one edge of each of the transparent electrodes, respectively.
The transparent electrodes 12Y and 12Z are commonly formed of indium-tin-oxide (ITO) on the top substrate 10. The metal bus electrodes 13Y and 13Z are commonly formed of metal such as Cr on the transparent electrodes 12Y and 12Z to reduce reduction in a voltage caused by the transparent electrodes 12Y and 12Z having high resistance. A top dielectric layer 14 and a protective layer 16 are laminated on the top substrate 10 on which the scan electrode Y and the sustain electrode Z are formed in parallel. Wall charges generated during plasma discharge are accumulated on the top dielectric layer 14. The protective layer 16 prevents the top dielectric layer 14 from being damaged by sputtering generated during plasma discharge and improves efficiency of emitting secondary electrons. MgO is commonly used as the protective layer 16.
A bottom dielectric layer 22 and a partition wall 24 are formed on the bottom substrate 18 on which the address electrode X is formed. The surfaces of the bottom dielectric layer 22 and the partition wall 24 are coated with a fluorescent body layer 26. The address electrode X is formed to intersect the scan electrode Y and the sustain electrode Z. The partition wall 24 is formed to run parallel with the address electrode X to prevent the UV rays and the visible rays generated by discharge from leaking to an adjacent discharge cell. The fluorescent body layer 26 is excited by the UV rays generated during plasma discharge to generate any one visible ray among red, green, and blue visible rays. An inactive mixed gas is implanted into a discharge space provided between the top and bottom substrates 10 and 18 and the partition wall 24.
In order to realize gray scales of an image, a PDP divides a frame into various sub fields having a different number of light emissions to perform time division driving. Each sub field is divided into an initializing period for initializing the entire screen, an address period for selecting a scan line and for selecting a cell from the selected scan line, and a sustain period for realizing gray scales in accordance with the number of times the discharge is made.
Here, the initializing period is divided into a set up period to which a rising ramp waveform is supplied and a set down period to which a falling ramp waveform is supplied. For example, when an image is displayed by 256 gray scales, as illustrated in FIG. 2, a frame period (16.67 ms) corresponding to 1/60 second is divided into eight sub fields SF1 to SF8. As described above, each of the eight sub fields SF1 to SF8 is divided into the initializing period, the address period, and the sustain period. Meanwhile the initializing period and the address period of the respective sub fields are the same, and the sustain period in each sub field increases in the ratio of 2n(n=0, 1, 2, 3, 4, 5, 6, and 7) as the sub field number increases.
FIG. 3 illustrates an apparatus for driving a PDP according to a background art.
Referring to FIG. 3, the apparatus for driving a PDP includes an address driving part 32 for driving address electrodes X1 to Xk provided on a plasma panel 30, a scan driving part 34 for driving scan electrodes Y1 to Yn provided on the panel 30, and a sustain driving part 36 for driving sustain electrodes Z1 to Zn provided on the panel 30.
The scan driving part 34 supplies a reset pulse, a scan pulse, and a sustain pulse to the scan electrodes Y1 to Yn. Here, the reset pulse and the sustain pulse are commonly supplied to all of the scan electrodes Y1 to Yn and the scan pulse is sequentially supplied to the scan electrodes Y1 to Yn.
The address driving part 32 generates data pulses (driving voltage) corresponding to image data provided from the outside and supplies them to the address electrodes X1 to Xk. Here, the data pulses are supplied to be synchronized with the scan pulse sequentially supplied to the scan electrodes Y1 to Yn.
The sustain driving part 36 supplies an electrode negative voltage (an electrode negative bias voltage) and the sustain pulse (the driving voltage) to the sustain electrodes Z1 to Zn. Here, the electrode negative voltage and the sustain pulse are commonly supplied to all of the sustain electrodes Z1 to Zn.
FIG. 4 illustrates a data integrated circuit (IC) in the driving apparatus of FIG. 3 according to the background art.
Referring to FIG. 4, in the driving apparatus of FIG. 3, the address driving part 32 includes one or more data ICs 40 having i output parts 42 electrically connected to address electrodes X1-Xi of the address electrodes X1-Xk, where i is a natural number. Although not shown, the output parts 42 receive a driving voltage (data pulses) Vh corresponding to image data input to the address driving part 32, and supply it to the address electrodes X1-Xi. Also a first end terminal 44 and a second end terminal 46 are provided on both ends of the data IC 40. The first end terminal 44 receives a ground voltage GND from the outside and supplies the received GND to the output parts 42 near the first end terminal 44. The second end terminal 46 also receives a ground voltage GND from the outside and supplies the received ground voltage GND to the output parts 42 near the second end terminal 46. The use of the first and second end terminals 44 and 46 to receive the ground voltage GND is known. The respective output parts 42 that received the driving voltage Vh and the ground voltage GND supply the data pulses corresponding to the image data to the address electrodes X1-Xi connected thereto.
According to the background art PDP, in order to cause sustain discharge, the sustain pulse having a high voltage value is alternately supplied to the scan electrodes Y and the sustain electrodes Z during the sustain period. Here, the sustain pulse having the high voltage value passes through the discharge cells that are equivalent to capacitors and is supplied to the output parts 42 of the data IC 40.
However, in the background art PDP, the brightness displayed by the address electrodes X connected to the output parts 42 positioned in the center of the data IC 40 is different from the brightness displayed by the address electrodes X connected to the output parts 42 positioned at the end portions of the data IC 40, such that spot-like noise is generated due to the difference in the brightness, which deteriorates display quality. Such a phenomenon occurs because the amount of the ground voltage GND supplied to the output parts 42 positioned at the center part of the data IC 40 is insufficient due to the fact that there are only two end terminals 44 and 46 that receive the ground voltage GND. As a result, the output parts 42 positioned at the center part of the data IC 40 are significantly affected by the high sustain voltage. In particular, the more the capacitor components of the discharge cells are and the larger the number of output parts 42 included in the data IC 40 is, the more significant the difference in the brightness becomes. For instance, to provide a PDP having a high resolution, a large number of output parts 42 may be provided in the data IC 40. In that case, however, the above problem of inconsistent brightness on the panel occurs due to the configuration of the data IC, thereby deteriorating the picture quality of the panel. This problem is also prominent in PDPs that use a single scan method.